Installation methods and devices for laying pipes from a vertical position to a horizontal position are already known, and described in various publications. In the international patent application WO2006085739 there is provided a method for installing an offshore pipeline where the weight of an accessory and a launched pipeline connected to the accessory is transferred from a clamping device to a controlled load hoisting device while the accessory and launched pipeline remain in a firing line. After disengaging the clamping device from the pipeline, the clamping device is moved out of the firing line. The accessory and launched pipeline are lowered along the firing line by the controlled load hoisting device.
In U.S. Pat. No. 6,361,250, there is provided a system and method to lay sub-sea pipelines at great depth. There is provided a tower which is particularly suitable for laying rigid pipes at depths up to 3000 m, with maximum loading of 600 tons. Rigid pipes are laid without plastic deformation, flexible pipes can also be handled. The carriages used are individually motorized, and operate on e.g. a rack and pinion, permitting the pipes to be moved and held in position. Conveniently, welding takes place at deck level. Demountable tower sections allow one tower to be used on another ship when necessary.
Further, in patent application US2007/0189857, there is disclosed a pipe laying tower with an upper clamping element vertically displaceable along a frame, and a lower clamping element supported on a vessel support structure. As the lower clamping element is not part of the J-lay frame, but is supported on the vessel support structure, the weight of the tower itself is reduced. This allows easy mounting of the lightweight frame portions and reduces modifications and structural reinforcements. Integration of the lower clamping block on the vessel support structure provides a low vertical center of gravity, reducing the motion-induced support loads on the vessel and providing for increased stability.
Such systems, however, require very good metocean conditions; the handling is time consuming and hence they provide expensive solutions. According to the present invention, there is provided a device and an offshore installation method to install a flexible hose offshore, which offer a large operation window as the operation can keep on going under high sea states such as for instance a sea state of 3 meters significant wave height.
The system according to the invention presents solutions that also increase the safety during installation, ease the access to personnel, and facilitate the key operations during installation.